CHAPTER
9 Chemical Equilibrium
Animation 9.1 : synthesis
source and credit: wikipe
,9. Chemical Equilibrium eLea
Students Learning Outcomes
Students will be able to:
• Define chemical equilibrium in terms of a reversible reaction. (Understanding);
• Write both the forward and the reverse reaction and describe the macroscopic
characteristics of each. (Applying);
• Define Law of Mass Action. (Understanding);
• Derive an expression for the equilibrium constant and its units. (Applying);
• State the necessary condition for the equilibrium and the ways that equilibrium can
recognized. (Understanding) and
• Write the equilibrium constant expression of a reaction.
Introduction
Generally, we presume that most chemical and physical changes proceed to comp
complete reaction is one in which all reactants have been converted into products. H
most chemical reactions do not go to completion because products react themselve
the reactants. As a result, after sometime no further change takes place. Quantities of r
and products remain unchanged and it seems that the reaction has stopped. In fa
reactions do not stop; rather they take place on both directions at equal rate and a
equilibrium state. Such reactions are called reversible reactions.Many examples of
and chemical equilibrium are found in nature.
We owe our existence to equilibrium phenomenon taking place in atmos
inhale oxygen and exhale carbon dioxide, while plants consume carbon di
release oxygen. This natural process is responsible for the existence of life on
Many environmental systems depend for their existence on delicate equilibrium phen
For example, concentration of gases in lake water is governed by the principles of equ
The lives of aquatic plants and animals are indirectly related to concentration of d
oxygen in water.
2
, 9. Chemical Equilibrium eLea
9.1 REVERSIBLE REACTION AND DYNAMIC EQUILIBRIUM
In a chemical reaction, the substances that combine are called reactants and the new s
formed are called products. For example, when H2 and O2 (reactants) combine they for
(product).
Most of the reactions, in which the products do not recombine to form reactants, are called irr
reactions. They are supposed to complete and are represented by putting a single arro
between the reactants and products.
On the other hand, reactions in which the products can recombine to form reactants
reversible reactions. These reactions never go to completion. They are represented by
arrow ( m) between reactants and products. These reactions proceed in both ways
consist of two reactions; forward and reverse. So, a reversible reaction is one whi
made to proceed in either direction depending upon the conditions.
3
9 Chemical Equilibrium
Animation 9.1 : synthesis
source and credit: wikipe
,9. Chemical Equilibrium eLea
Students Learning Outcomes
Students will be able to:
• Define chemical equilibrium in terms of a reversible reaction. (Understanding);
• Write both the forward and the reverse reaction and describe the macroscopic
characteristics of each. (Applying);
• Define Law of Mass Action. (Understanding);
• Derive an expression for the equilibrium constant and its units. (Applying);
• State the necessary condition for the equilibrium and the ways that equilibrium can
recognized. (Understanding) and
• Write the equilibrium constant expression of a reaction.
Introduction
Generally, we presume that most chemical and physical changes proceed to comp
complete reaction is one in which all reactants have been converted into products. H
most chemical reactions do not go to completion because products react themselve
the reactants. As a result, after sometime no further change takes place. Quantities of r
and products remain unchanged and it seems that the reaction has stopped. In fa
reactions do not stop; rather they take place on both directions at equal rate and a
equilibrium state. Such reactions are called reversible reactions.Many examples of
and chemical equilibrium are found in nature.
We owe our existence to equilibrium phenomenon taking place in atmos
inhale oxygen and exhale carbon dioxide, while plants consume carbon di
release oxygen. This natural process is responsible for the existence of life on
Many environmental systems depend for their existence on delicate equilibrium phen
For example, concentration of gases in lake water is governed by the principles of equ
The lives of aquatic plants and animals are indirectly related to concentration of d
oxygen in water.
2
, 9. Chemical Equilibrium eLea
9.1 REVERSIBLE REACTION AND DYNAMIC EQUILIBRIUM
In a chemical reaction, the substances that combine are called reactants and the new s
formed are called products. For example, when H2 and O2 (reactants) combine they for
(product).
Most of the reactions, in which the products do not recombine to form reactants, are called irr
reactions. They are supposed to complete and are represented by putting a single arro
between the reactants and products.
On the other hand, reactions in which the products can recombine to form reactants
reversible reactions. These reactions never go to completion. They are represented by
arrow ( m) between reactants and products. These reactions proceed in both ways
consist of two reactions; forward and reverse. So, a reversible reaction is one whi
made to proceed in either direction depending upon the conditions.
3
